Hi Kerrie, firstly, I was just looking at an owl I have that has very similar optical 'trickery' as your owl.... then I open GMB and there is your question!!
The one I have is smaller, 3" tall, and the base is in pristine condition, no age related wear at all.
However, the eyes are made by the way the back is star cut....
Mine does have a groove for the nose and also a label, which may help, if only to eliminate a maker.
Also mine is clear crystal
Yours looks as though it might be Neodymium glass.... have you tried looking at it under fluorescent lighting (the kind you have in kitchen strip lighting over the counter tops) or under energy-saving light bulbs .?
Here are a couple of pictures of mine:
Rosie.